The present invention relates to a structure for interconnecting two elongated elements such as two parts of a bridge deck separated by an expansion joint, the parts for example made from prestressed concrete, or more generally of an assembly forming a very long beam.
Numerous prestressed-concrete bridges have been constructed by cantilevering with the aid of movable equipment, or by assembling prefabricated elements, the deck being constructed in successive stages symmetrically relative to the piers.
In the first structures of this type, an expansion joint was provided at the center of each span, at the joint between two facing cantilever arms. A mechanical device traversing the joint was provided to permit the expansions of the deck whilst preventing the relative vertical displacement of the two cantilever arms, the continuity of the roadway for highway bridges or the continuity of the rails for railroad bridges thus being ensured.
Such structures are simple to design and construct. However, the influence of the differential deformations of the concrete (creep) becomes very important when the spans exceed 40 to 50 meters, and considerable annular discontinuities in the vertical plane have appeared on numerous structures at all the expansion joints.
The most frequent angular discontinuity corresponds to an upward-pointing angle between the two deck parts, in other words with the joint forming a low point, but a downward-pointing angle can also occur, and irregularities in the material or the stresses can also result in angular deviations in the horizontal plane of the deck, or in relative torsion of one deck part with respect to the other.
In order to overcome the problem, mechanical continuity of the deck has been achieved at the center of the spans, the cantilever arms being assembled together to form a continuous beam.
For a very long structure, expansion joints must, however, be provided at gaps of a few hundred meters in order to ensure the free expansion of the deck.
If the joint is provided at the center of a span, the abovementioned problem of the angular discontinuity of the deck reoccurs. This means that the joint must be moved to a point one quarter of the width of the span, at the point of inflexion of the deformations, where the variations in moment created by the live loads are minimal. The solution is highly satisfactory in theory but its application in practice seriously complicates the construction as, during the latter, the mechanical continuity through the joint must be ensured to allow the remainder of the deck to be put in place.
In the German Patent Application No. 2712091 to Fritz Leonhardt, it was proposed to use jacks acting in the lengthwise direction of the bridge and arranged at points distant from the central part of the joint plane in order to exert forces tending to separate or bring together the facing parts of the deck. This arrangement makes it possible to counteract the appearance of angular discontinuities, but it cannot prevent dislocations in a transverse plane passing through the joint and resulting, in particular, from a relative vertical displacement, or a relative torsion, of the two deck parts.
The prior art thus makes it possible to counteract either vertical dislocations or angular discontinuities but it does not provide an adequate solution to the entire problem.
Similar problems occur at the location of the expansion joint which separates the end of the deck from the adjacent abutment. In what follows, two parts of a bridge deck will be referred to but it should be understood that it would not be going beyond the scope of the invention if one of these two parts consisted of one end of the deck and the other of the end of the adjacent abutment.
The initial object of the present invention is to provide a simple and economical solution to the entire problem of the discontinuities and dislocations of a bridge deck where at the location of the expansion joints. However, the invention can apply to any assembly forming a very long beam, and comprising at least two parts separated by an expansion joint.